Liquid cooling arrangement for electric machines

ABSTRACT

A cooling arrangement for electric machines comprising a heat storing element provided with generally C-shaped channels and a cooling tube so configured and sized as to be insertable in said C-shaped channels of said heat storing element is described herein. The cooling tube, once inserted in the channels is deformed to conform to the C-shaped channels, whereby heat stored in said heat storing element is extracted by circulating cooling fluid inside the cooling tube.

This is a division of Application No. 10/198,186, filed Jul. 18, 2002,now U.S. Pat. No. 6,819,016.

FIELD OF THE INVENTION

The present invention relates to electric machines. More specifically,the present invention is concerned with a liquid cooling arrangement forelectric machines.

BACKGROUND OF THE INVENTION

Electric machines, whether they are motors or generators, are well knownin the art. It is also widely known that electric machines generate heatas a by-product and that this heat must be somehow extracted from themachine to improve the performances of the machine and prevent earlydegradation of the machine.

Conventionally, electric machines are often air-cooled. This is easilydone by providing apertures in the body of the machine to let air beforced therein. The efficiency of such a cooling arrangement is poorsince air is a generally non-efficient cooling fluid. Furthermore, someelectric machines operate in environment that are such that it is notpossible to provide an electric machine with apertures.

Electric machines using cooling fluid have also been designed. Forexample, European Patent Number 0,503,093 entitled “Liquid CoolingDevice of Motor” and naming Nakamura as inventor discloses an electricmotor where the laminations are provided with apertures allowing anaxial flow of cooling liquid when the laminations are assembled. Adrawback of Nakamura's system is the risk of failure of the motor causedby leaks. Indeed, a failure-causing link could spring should the sealbetween adjacent laminations fail.

OBJECTS OF THE INVENTION

An object of the present invention is therefore to provide an improvedliquid cooling arrangement for electric machines.

SUMMARY OF THE INVENTION

More specifically, there is provided a cooling arrangement for electricmachines comprising a heat storing element provided with generallyC-shaped channels; a cooling tube so configured and sized as to beinsertable in the C-shaped channels of the heat storing element; thecooling tube, once inserted in the channels, being deformed to conformto the C-shaped channels; and heat stored in the heat storing elementbeing extractable by the cooling tube, wherein the heat storing elementis formed of laminations of a stator of the electric machine.

It is further provided an electric machine comprising a generally hollowcylindrical stator; a rotor rotatably mounted to the stator; a coolingarrangement including a heat storing element provided with generallyC-shaped channels; the heat storing element being associated with thestator to extract heat therefrom; a cooling tube so configured and sizedas to be insertable in the C-shaped channels of the heat storingelement; wherein the cooling tube, once inserted in the channels isdeformed to conform to the C-shaped channels; heat stored in the heatstoring element is extractable by the cooling tube; the heat storingelement is formed of laminations of the stator; and the C-shapedchannels are provided on an inner surface of the stator.

It is to be noted that the expression “electric machine” is to beconstrued herein as encompassing both electric motors and electricgenerators disregarding the technology used in these machines.

Other objects, advantages and features of the present invention willbecome more apparent upon reading of the following non-restrictivedescription of preferred embodiments thereof, given by way of exampleonly with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the appended drawings:

FIG. 1 is a perspective, partly exploded view, of the stator of anelectric machine provided with a cooling arrangement according to afirst embodiment of the present invention;

FIG. 2 is a perspective view of the stator of FIG. 1 where the coolingtube is inserted in channels provided therein;

FIG. 3 is a perspective view illustrating the completed stator of FIG.1;

FIG. 4 is a sectional view illustrating the insertion of sections of thecooling tube in the channels provided in the stator;

FIG. 5 a is a sectional view illustrating the cooling tubes inserted inthe channels and deformed according to a first pattern to permanentlymount them in the channels;

FIG. 5 b is a sectional view illustrating the cooling tubes inserted inthe channels and deformed according to a second pattern to permanentlymount them in the channels;

FIG. 6 is an exploded view of a cooling arrangement according to asecond embodiment of the present invention;

FIG. 7 is a side elevational view of the cooling arrangement of FIG. 6illustrating the deformation of the cooling tube in the channels of theheat storing element;

FIG. 8 is a perspective, partly exploded view, of the coolingarrangement of FIG. 6 and the stator of an electric machine; and

FIG. 9 is a side elevational view of the assembled stator including thecooling arrangement of FIG. 6.

DESCRIPTION OF THE EMBODIMENTS

In a nutshell, a first embodiment of the present invention, illustratedin FIGS. 1 to 5 b, uses the laminations of the stator as a heat storingelement provided with generally C-shaped channels in which a coolingtube is mounted. In operation, cooling fluid is circulated in thecooling tube to extract heat stored in the laminations.

A second embodiment of the present invention, illustrated in FIGS. 6 to9, uses a separate heat storing element also provided with generallyC-shaped channels in which a cooling tube is mounted. The heat storingelement is then inserted in the stator of an electric machine with thecooling tube in contact with both the heat storing element and thestator. In operation, cooling fluid is circulated in the cooling tube toextract heat accumulated in the heat storing element and in the stator.

Turning now to FIGS. 1 to 5 b a cooling arrangement 10 according to thefirst embodiment of the present invention will now be described.

FIG. 1 shows a stator 12 of an electric machine (not shown). The stator12 is made of a plurality of identical laminations stacked together. Thestator 12 is generally cylindrical and includes rectangular externalchannels 14 in which coils 16 are mounted. It is to be noted that thestator 12 is a so-called internal stator, i.e. that the rotor (notshown) is so mounted to the stator as to be coaxial and external to thestator 12.

The laminations of the stator 12 are used as a heat storing element, aswill be described hereinbelow.

The inside surface 18 of the stator 12 is provided with a plurality ofgenerally C-shaped channels 20.

The cooling arrangement 10 also includes a cooling tube 22 having agenerally circular cross-section and provided with an inlet 24 and anoutlet 26. As can be clearly seen in FIG. 1, the cooling tube 22 is sofolded as to form a serpentine.

As will be explained hereinbelow, the cooling tube is so configured andsized to be inserted in the C-shaped channels 20 of the stator 12.

FIG. 2 illustrates the cooling tube 22 inserted in the generallyC-shaped channels of the stator 12. As can be seen in this Figure, theserpentine folding of the cooling tube 22 is optionally configured sothat the rounded portions thereof extend outside of the stator 12. Thisarrangement may be interesting since is allows the rounded portions ofthe cooling tube to be folded outwardly as illustrated in FIG. 3 toincrease the contact surface between the cooling tube 22 and the stator12.

Turning now to FIGS. 4 and 5 a, it can be better seen that each C-shapedchannel 20 has a generally closed C-shape configuration, i.e. that theopening of the channel is smaller than the widest portion of thechannel. It is also to be noted that the circular cross section of thecooling tube 22 is at most equals to the opening of the channel to allowits insertion therein.

To insert the cooling tube 22 in the channels 20, a first step is togenerally align the straight portions of the cooling tube 22 with acorresponding channel 20 of the stator 12, as can be seen in FIG. 4.This operation is facilitated by the possibility to significantly deformthe serpentine configuration of the tube 22 to allow its insertion intothe central opening of the stator 12.

The next insertion step is to deform the serpentine configuration of thecooling tube 22 so that each straight section is inserted in acorresponding channel (see arrows 28 in FIG. 4). The result of this stepis illustrated in dashed lines in FIG. 4.

To maintain the straight portions of the cooling tube 22 into thechannels 20, these straight portions are deformed to conform to thegenerally closed C-shaped configuration of the channels 20. To achievethis, a pressure is radially applied (see arrows 30 a in FIG. 5 a) ontothe cooling tube 22. This radial pressure causes the widening of thetube as can be seen from arrows 32. It is to be noted that according tothis first type of deformation of the cooing tube 22, the cooling tube22, once deformed, presents a slightly convex surface with respect tothe inner surface of the stator 12.

It is to be noted that, optionally, a heat conducting and/or adhesivesubstance may be placed between the channel and the tube to provideimproved heat transfer between these elements.

It is also to be noted that while many materials can be used for thecooling tube 22, good results have been obtained by using copper tubing.

Turning now briefly o FIG. 5 b of the appended drawings a second type ofdeformation of the cooling tube 22 inside the channels 20 will bebriefly described. As can be seen from this figure, the second type ofdeformation of the cooing tube 22 presents a slightly concave surfacewith respect to the inner surface of the stator 12. Again, to achievethis, a pressure is radially applied (see arrows 30 b in FIG. 5 b) ontothe cooling tube 22.

This second type of deformation is believed interesting since, it wouldprevent unwanted loosening of the cooling tube inside the channels.

Turning now to FIGS. 6 to 9, a cooling arrangement 100 according to asecond embodiment of the present invention will now be described.

As mentioned hereinabove, the cooling arrangement 100 uses a separateheat storing element 102. This heat storing element 102 includes anexternal and generally circumferential channel 104 into which a coolingtube 106 having a serpentine configuration may be inserted as will bedescribed hereinbelow. It is to be noted that while it is not expresslyillustrated in the appended figures, the channel 104 has a serpentineconfiguration generally corresponding to the serpentine configuration ofthe cooling tube 106.

The cooling tube 106 has a generally serpentine configuration andincludes an inlet 110 and an outlet 112.

As can be better seen from FIGS. 7 and 9, the C-shaped channel 104 has agenerally open C-shape configuration, i.e. that the opening of thechannel is the same width as the widest portion of the channel.

Again, the insertion of the cooling tube 106 into the channel 106 isgenerally straightforward. The cooling tube 106 is first positioned sothat is adequately faces the channel 104. The tube is then inserted inthe channel (see the tube 106 in full lines in FIG. 7). The final stepis to deform the cooling tube so that it does not protrudes from theexternal surface of the heat storing element 102 (see the tube 106 indashed lines in FIG. 7). This is done by applying an inwardly radialpressure (see arrows 114), which forces the tube 106 to conform to thechannel 104 (see arrows 116).

As mentioned hereinabove, a heat conducting and/or adhesive substancemay optionally be placed between the channel and the tube to provideimproved heat transfer between these elements.

Turning now briefly to FIG. 8 of the appended drawings, once the coolingtube 106 is properly inserted in the heat storing element 102, thecooling arrangement 100 may be inserted in the stator 118 of an electricmachine (not shown).

FIG. 9 is a sectional view of the cooling arrangement 100 mounted in thestator 118. One skilled in the art will appreciate that since thecooling tube 106 contacts both the heat storing element 102 and thestator 118, heat from these two elements will be extracted by thecooling fluid circulating in the cooling tube 106.

It is to be noted that even though the two embodiments of the presentinvention have been illustrated as being part of an electric machineprovided with an internal stator and an external rotor (not shown), oneskilled in the art could easily adapt the present invention to be usedin an electric machine having an external stator and an internal rotor.

It is also to be noted that while the embodiments of the presentinvention have been described hereinabove as using an open cooling tubewhere a flow of fluid is used to extract the heat from the heat storingelement, other cooling technologies, such as, for example, the heat pipetechnology could be used. Indeed, one skilled in the art would have noproblem designing or modifying conventionally known heat pipes so thatthey can be mounted in the C-shaped channels. For example, in the firstembodiment illustrated in FIGS. 1–5 b, separate straight heat pipes (notshown) could be inserted in each longitudinal channel 20, and in thesecond embodiment illustrated in FIGS. 6–9, a continuous heat pipes (notshown) could be inserted in the channel 114.

It is also to be noted that the two embodiments illustrated respectivelyin FIGS. 1 to 5 b and 6 to 9 could be combined to increase the coolingpossibilities.

Although the present invention has been described hereinabove by way ofpreferred embodiments thereof, it can be modified, without departingfrom the spirit and nature of the subject invention as defined in theappended claims.

1. A cooling arrangement for electric machines comprising a heat storing element provided with generally C-shaped channels; a cooling tube so configured and sized as to be insertable in the C-shaped channels of the heat storing element; the cooling tube, once inserted in the channels, being deformed to conform to the C-shaped channels; and heat stored in the heat storing element being extractable by the cooling tube, wherein said heat storing element is formed of laminations of a stator of the electric machine.
 2. The cooling arrangement as recited in claim 1, wherein said stator has a generally tubular configuration and wherein said C-shaped channels are provided on an inner surface of said stator.
 3. The cooling arrangement as recited in claim 2, wherein said channels are generally parallel to a longitudinal axis of the generally tubular stator.
 4. The cooling arrangement as recited in claim 3, wherein: said cooling tube is so folded as to form a serpentine; when inserted in said channels of said heat storing element, said cooling tube presents projecting rounded portions that are folded onto said heat storing element; whereby a contact surface between the cooling tube and the heat storing element is maximized.
 5. The cooling arrangement as recited in claim 2, wherein said channels are generally perpendicular to a longitudinal axis of the generally tubular stator.
 6. The cooling arrangement as recited in claim 2, wherein said channels have a closed C-shape configuration.
 7. The cooling arrangement as recited in claim 2, wherein said C-shaped channels and said cooling tube is so dimensioned that when said cooling tube is inserted in said channels and deformed, said cooling tube is substantially flush with the inner surface of the stator.
 8. The cooling arrangement as recited in claim 2, wherein said C-shaped channels and said cooling tube is so dimensioned that when said cooling tube is inserted in said channels and deformed, said cooling tube presents a concavity with respect to the inner surface of the stator.
 9. An electric machine comprising: a generally hollow cylindrical stator; a rotor rotatably mounted to said stator; a cooling arrangement including: a heat storing element provided with generally C-shaped channels; said heat storing element being associated with said stator to extract heat therefrom; a cooling tube so configured and sized as to be insertable in said C-shaped channels of said heat storing element; wherein said cooling tube, once inserted in said channels is deformed to conform to the C-shaped channels; heat stored in said heat storing element is extractable by said cooling tube; said heat storing element is formed of laminations of said stator; and said C-shaped channels are provided on an inner surface of said stator. 